Then, I go to the xorg meta-package. I scroll down to the things it depends on and I select them manually, and I dig down into the dependancies and adjust things. For example, somewhere there a package will depend on _either_ an -all package or a device-specific package. Left on its own, it will pull in the -all whereas I can mark the device spcific package for manual and deselect the -all.
Thanks. I'll give it a go tomorrow and will report back on progress.